The knee joint is a tri-compartmental joint consisting of the medial and lateral compartments which make up the tibiofemoral joint (“TFJ”) and the patellofemoral compartment which makes up the patellofemoral joint (“PFJ”). The PFJ more specifically includes the patella and the trochlear groove of the femur. Noninflamatory degenerative joint disease, such as osteoarthritis, inflammatory joint disease, such as rheumatoid arthritis, traumatic injuries and structural abnormalities may affect any combination of the aforementioned knee compartments. Severe pain may result where the articular cartilage of the patella and/or the femoral trochlear groove is eroded or otherwise damaged and natural motion of the patella along the trochlear groove is impeded. For patients with erosion or damage confined to the PFJ, or for patients with a history of chronic patella dislocations, a patellofemoral joint replacement may offer a beneficial alternative to total joint replacement. Moreover, a patellofemoral joint replacement generally provides pain relief or improved patella tracking while preserving significantly more bone than a total joint replacement.
In total joint replacement, all three compartments are effected whereby portions of a patient's trochlear groove, medial and lateral condyles, and tibial plateau are generally each resected and substituted for by one or more joint prostheses. In contrast, in PFJ replacement, generally only the patella and the trochlear groove are replaced. A major benefit of PFJ replacement over total joint replacement is bone preservation, which may reduce recovery time and post-operative pain. Another advantage of bone preservation is that the joint line may be maintained resulting in a more normal functioning knee. Further advantages may include less cost and procedure duration, which reduces the likelihood of contracting an infection and positively affects recovery time.
Current PFJ replacement systems employ several types of instruments for removing bone in the trochlear groove region of the femur. For example, forming bone adjacent the intercondylar notch of the trochlear groove may occur with a rongeur, osteotome, rasp, reciprocating or oscillating saw, burr, or a combination of all of these instruments. However, a common characteristic of the use of these instruments in current PFJ replacement is that they are generally free-hand instruments that primarily rely on the skill of the surgeon handling them. However, even a skilled surgeon may have trouble duplicating results where speed and precision are critical. Therefore, one of the biggest drawbacks of current instrumentation is that each provides no true anatomically based means for guiding the surgeon to restore the trochlear groove or patellar track to ensure proper patellofemoral kinematics. Further, certain existing patellofemoral implants have asymmetric designs and few sizing options, which frequently results in a poor anatomic fit. Guided formation of this bone and proper selection of patellofemoral implants are important for implant stability and sustainability, as well as assuring natural patellar tracking and restoration of the “Q angle” defined by the lines representing the pull of the quadriceps muscle on the patella and the axis formed by the patella tendon between the patella and tibial tubercle.
Therefore, there is a need for guided PFJ reconstruction instrumentation that provides accurate, reproducible results and a varied selection of anatomic patellofemoral implantation with improved patellar tracking characteristics that collectively provide added natural post-operative knee kinematics.